1. Field of the Invention
This invention relates to a filter for cigarettes. In one aspect it relates to a filter with novel ventilating means. In another respect the invention relates to a filter for a ciagarette having flow directing grooves formed therein for directing ventilating air to the mouth end of the filter and concurrently delivering filtered smoke through the filter to the mouth end of the filter. In yet another aspect, the present invention relates to a cigarette filter of the class described wherein, under certain smoking conditions, at least some ventilating air passes from the flow directing grooves and into the filter to co-mingle with and dilute the smoke flowing in the filter before it reaches the mouth end of the filter.
2. Description of the Prior Art
It is well known in the art to add filters to cigarettes wherein the filters are provided with ventilation means to bring ambient air into the filter to dilute the smoke stream passing therethrough. The dilution of the smoke stream reduces the quantity of smoke particulates as well as the gas phase components which are delivered to the smoker's mouth. A number of means have been proposed and are utilized for introducing ventilating air into the cigarette. For example, the wrapper for the tobacco of a cigarette can be made from a porous material which allows for introduction of air along the entire length of the cigarette where it mixes with the smoke stream passing therethrough thereby diluting the smoke in the stream. Also the cigarette wrapper may be perforated at selected locations along the length of the cigarette which provides ports in the cigarette through which ventilating air enters. Even further, it is known to perforate the wrapper of the filter of a filtered cigarette to allow ventilating air to enter the filter and dilute the smoke stream passing through the filter. There have also been a number of suggestions for incorporating grooves within the filter of a filter cigarette to facilitate the addition of ventilating air into the smoke stream.
For example, U.S. Pat. No. 3,596,663 relates to a tobacco smoke filter provided with a corrugated porous plug wrap surrounding a filter element which is circumscribed by tipping paper having flow-through perforations. The ventilating air enters into the filter element and the grooves through the perforations in the tipping paper and progresses to the smoker's mouth. And, U.S. Pat. No. 4,256,122 teaches a filter for a cigarette which includes grooves extending longitudinally along the outer surface of a filter rod circumscribed by a non-porous plug wrap and the rod and wrap are enclosed with ventilating tipping paper so that in use only ventilating air travels down the grooves and only smoke travels through the filter. Other patents which relate to cigarette filters having grooves circumscribing the filter element for the introduction of ventilating air into the cigarette filter include U.S. Pat. No. 3,577,995; U.S. Pat. No. 3,752,347; U.S. Pat. No. 3,490,461; U.S. Pat. No. 3,788,330; U.S. Pat. No. 3,773,053; U.S. Pat. No. 3,752,165; U.S. Pat. No. 3,638,661; U.S. Pat. No. 3,608,561; U.S. Pat. No. 3,910,288; U.S. Pat. No. 4,256,122 and U.S. Pat. No. 3,910,288.